Preheat the oven to 415 degrees F.

Trim the top off of the kabocha squash. Drizzle the flesh with olive oil and use your hands to coat it. Sprinkle with salt and place cut-side down on a baking sheet. Roast in the preheated oven 55 to 65 minutes, or until kabocha squash is very soft when poked with a fork.

Scoop the flesh out of the kabocha squash and place it in a bowl to cool. Once cool, add the kabocha squash to a high-powered blender along with the rest of the ingredients for the filling. Blend until well-combined. Transfer filling mixture to a 9-inch round casserole dish (or 2-quart rectangular casserole dish) and preheat the oven to 375 degrees F.

Stir together all of the ingredients for the topping until well combined. Evenly spread the topping mixture over the kabocha squash - it’s fine to have large clumps.

Bake at 375 degrees for 40 to 50 minutes, until the topping is golden-brown and filling is bubbling, then turn off the oven and allow casserole to sit an additional 10 minutes. Remove from the oven and cool for 15 minutes before serving.

Store leftovers in a sealed container and refrigerate up to 7 days.